Simplify the following expression: $y = \dfrac{-90k - 60}{30k + 10}$ You can assume $k \neq 0$.
Explanation: Find the greatest common factor of the numerator and denominator. The numerator can be factored: $-90k - 60 = - (2\cdot3\cdot3\cdot5 \cdot k) - (2\cdot2\cdot3\cdot5)$ The denominator can be factored: $30k + 10 = (2\cdot3\cdot5 \cdot k) + (2\cdot5)$ The greatest common factor of all the terms is $10$ Factoring out $10$ gives us: $y = \dfrac{(10)(-9k - 6)}{(10)(3k + 1)}$ Dividing both the numerator and denominator by $10$ gives: $y = \dfrac{-9k - 6}{3k + 1}$